There are two sorts of photoreceptor cells in retina:
Rods: The photoreceptor cells that contain rhodopsin pigment and related to night vision of eye i.e. vision under low light.
Cones: The cells which is responsible for photoception called photoreceptor cells that contain iodopsin, porpyrosin and cyanopsin pigments. These cells are related to the photopic vision and colour vision of eyes.
Hence, colour perception in humans is thanks to iodopsin in cone cells.
So, the right answer is 'Iodopsin pigment in cone cells'.